1. Field of the Invention
The present invention relates to an inkjet recording apparatus and a head maintenance method, and more particularly to maintenance technology for an inkjet head.
2. Description of the Related Art
An inkjet recording apparatus which records color images by ejecting color inks onto a recording medium from a plurality of nozzles provided in an inkjet head maintains uniform image quality by carrying out a preliminary ejection operation at fixed intervals from the inkjet heads of the respective colors. A general inkjet recording apparatus is composed in such a manner that preliminary ejection (purging) is carried out by moving the head to a special preliminary ejection position or capping position. However, the head movement time limits the extent to which the preliminary ejection operation time can be shortened, and this is particularly marked in apparatuses using a line type head in which a plurality of nozzles are arranged in the breadthways direction of the recording medium.
On the other hand, a method has been proposed in which preliminary ejection is carried out onto a position on the recording medium where it is not noticeable, or onto a conveyance belt which conveys the recording medium. According to this method, it is not necessary to move the head each time a preliminary ejection operation is carried out, but if preliminary ejection is carried out onto the recording medium, then the position where preliminary ejection can be performed is limited to a narrow region, such as the margins, and sufficient purging cannot be performed for each of the heads. Furthermore, if forming images on a recording medium of narrower width than the ejection width of the line type head, it is difficult to perform preliminary ejection throughout the whole width of the head. Moreover, if performing preliminary ejection onto a conveyance belt, it is necessary to clean the conveyance belt each time preliminary ejection is carried out.
Japanese Patent Application Publication No. 2006-159556 discloses a liquid ejection apparatus in which a plurality of preliminary ejection holes through which liquid ejected by preliminary ejection can pass, and a liquid receiving section which receives ink that has passed through the preliminary ejection holes, are provided in a conveyance belt which conveys a medium. By suctioning the ink ejected by preliminary ejection by means of this structure, the ink purged into the preliminary ejection holes is recovered.
Japanese Patent Application Publication No. 2006-239871 discloses an inkjet recording apparatus based on a drum conveyance system in which a liquid receiving section is provided in order to receive ink ejected by preliminary ejection in a portion of a rotating drum in the circular circumferential direction, an ink storage unit which stores ink is provided in the liquid receiving section, and the ink storage unit is covered with a covering section formed on the outermost circumferential section of the rotating drum so as to cover the outer circumferential side of the rotating drum in the radial direction. By means of this structure, scattering of the ink ejected into the liquid receiving section by preliminary ejection is prevented.
However, in the liquid spray apparatus described in Japanese Patent Application Publication No. 2006-159556, a composition is adopted in which paper is suctioned and conveyed while suctioning the ink ejected by preliminary ejection, and consequently there is a large amount of sliding between the conveyance belt and the liquid receiving section, and operational errors such as slippage, and problems such as stretching of the conveyance belt, or deformation or rupture of the preliminary ejection holes, or the like, are liable to occur. Furthermore, if a plurality of heads are provided so as to correspond to a plurality of colors, then the liquid receiving section needs the sufficient length in the conveyance direction and the apparatus is liable to become larger in size.
In the inkjet recording apparatus disclosed in Japanese Patent Application Publication No. 2006-239871, a covering section is provided in an ink ejection unit, and therefore it is possible to reduce the scattering of ink from the ink storage unit due to centrifugal force caused by the rotation of the rotating drum, but there is a possibility of scattering of ink which has adhered to the periphery of the opening provided in the circumferential surface of the rotating drum. Furthermore, it is difficult to recover ink (ink mist) which has been propelled into the air.